Staff: Mentor

If there is no chemical reaction, there is nothing that could change the temperature. Okay, you still have the mechanical energy of the material sinking to the bottom, but that is completely negligible.

The temperature may change just from the physical contact between the solid and liquid simply through conduction of heat. In general correlating temperature changes with chemical or physical processes requires knowledge about what processes are occurring during the temperature change. If there is no chemical or physical process occurring then the temperature change is not giving you information about that process.

Also heats of formation refer to compounds being formed from their constituent elements, not being dissolved or dissociated in solution. These values are typically tabulated as standard heats of formation in various thermodynamic tables.